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Runoff Curve Number
The runoff curve number (also called a curve number or simply CN) is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. The curve number method was developed by the USDA Natural Resources Conservation Service, which was formerly called the ''Soil Conservation Service'' or ''SCS'' — the number is still popularly known as a "SCS runoff curve number" in the literature. The runoff curve number was developed from an empirical analysis of runoff from small catchments and hillslope plots monitored by the USDA. It is widely used and is an efficient method for determining the approximate amount of direct runoff from a rainfall event in a particular area. Definition The runoff curve number is based on the area's hydrologic soil group, land use, treatment and hydrologic condition. References, such as from USDA indicate the runoff curve numbers for characteristic land cover descriptions and a hydrologic soil group. The runoff equation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Empirical
Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences and plays a role in various other fields, like epistemology and law. There is no general agreement on how the terms ''evidence'' and ''empirical'' are to be defined. Often different fields work with quite different conceptions. In epistemology, evidence is what justifies beliefs or what determines whether holding a certain belief is rational. This is only possible if the evidence is possessed by the person, which has prompted various epistemologists to conceive evidence as private mental states like experiences or other beliefs. In philosophy of science, on the other hand, evidence is understood as that which ''Scientific method#Confirmation, confirms'' or ''disconfirms'' Hypothesis#Scientific hypothesis, scientific hypotheses and arbitrates ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is called a hydrologist. Hydrologists are scientists studying earth or environmental science, civil or environmental engineering, and physical geography. Using various analytical methods and scientific techniques, they collect and analyze data to help solve water related problems such as environmental preservation, natural disasters, and water management. Hydrology subdivides into surface water hydrology, groundwater hydrology (hydrogeology), and marine hydrology. Domains of hydrology include hydrometeorology, surface hydrology, hydrogeology, drainage-basin management, and water quality, where water plays the central role. Oceanography and meteorology are not included because water is only one of many important aspects within those fields. H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Runoff
Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the soil is saturated by water to its full capacity, and the rain arrives more quickly than the soil can absorb it. Surface runoff often occurs because impervious areas (such as roofs and pavement) do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or man-made processes. Surface runoff is a major component of the water cycle. It is the primary agent of soil erosion by water. The land area producing runoff that drains to a common point is called a drainage basin. Runoff that occurs on the ground surface before reaching a channel can be a nonpoint source of pollution, as it can carry man-made contaminants or natural forms of pollution (such as rotting leaves). Man-made contaminants in runoff i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infiltration (hydrology)
Infiltration is the process by which water on the ground surface enters the soil. It is commonly used in both hydrology and soil sciences. The infiltration capacity is defined as the maximum rate of infiltration. It is most often measured in meters per day but can also be measured in other units of distance over time if necessary. The infiltration capacity decreases as the soil moisture content of soils surface layers increases. If the precipitation rate exceeds the infiltration rate, runoff will usually occur unless there is some physical barrier. Infiltrometers, permeameters and rainfall simulators are all devices that can be used to measure infiltration rates. Infiltration is caused by multiple factors including; gravity, capillary forces, adsorption and osmosis. Many soil characteristics can also play a role in determining the rate at which infiltration occurs. Factors that affect infiltration Precipitation Precipitation can impact infiltration in many ways. The am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water for hydroelectric power plants, crop irrigation, and suitable conditions for many types of ecosystems. The major cause of rain production is moisture moving along three-dimensional zones of temperature and moisture contrasts known as weather fronts. If enough moisture and upward motion is present, precipitation falls from convective clouds (those with strong upward vertical motion) such as cumulonimbus (thunder clouds) which can organize into narrow rainbands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation which forces moist air to condense and fall out as rainfall along the sides of mountains. On the leeward side of mountains, desert climates can exi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
USDA
The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of commercial farming and livestock food production, promotes agricultural trade and production, works to assure food safety, protects natural resources, fosters rural communities and works to end hunger in the United States and internationally. It is headed by the Secretary of Agriculture, who reports directly to the President of the United States and is a member of the president's Cabinet. The current secretary is Tom Vilsack, who has served since February 24, 2021. Approximately 80% of the USDA's $141 billion budget goes to the Food and Nutrition Service (FNS) program. The largest component of the FNS budget is the Supplemental Nutrition Assistance Program (formerly known as the Food Stamp program), which is the cornerstone of USDA's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Resources Conservation Service
Natural Resources Conservation Service (NRCS), formerly known as the Soil Conservation Service (SCS), is an agency of the United States Department of Agriculture (USDA) that provides technical assistance to farmers and other private landowners and managers. Its name was changed in 1994 during the presidency of Bill Clinton to reflect its broader mission. It is a relatively small agency, currently comprising about 12,000 employees. Its mission is to improve, protect, and conserve natural resources on private lands through a cooperative partnership with state and local agencies. While its primary focus has been agricultural lands, it has made many technical contributions to soil surveying, classification, and water quality improvement. One example is the Conservation Effects Assessment Project (CEAP), set up to quantify the benefits of agricultural conservation efforts promoted and supported by programs in the Farm Security and Rural Investment Act of 2002 (2002 Farm Bill). NRCS i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Empirical Method
Empirical research is research using empirical evidence. It is also a way of gaining knowledge by means of direct and indirect observation or experience. Empiricism values some research more than other kinds. Empirical evidence (the record of one's direct observations or experiences) can be analyzed quantitatively or qualitatively. Quantifying the evidence or making sense of it in qualitative form, a researcher can answer empirical questions, which should be clearly defined and answerable with the evidence collected (usually called data). Research design varies by field and by the question being investigated. Many researchers combine qualitative and quantitative forms of analysis to better answer questions that cannot be studied in laboratory settings, particularly in the social sciences and in education. In some fields, quantitative research may begin with a research question (e.g., "Does listening to vocal music during the learning of a word list have an effect on later memory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precipitation (meteorology)
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor (reaching 100% relative humidity), so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation but colloids, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers. Moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condense ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Land Use
Land use involves the management and modification of natural environment or wilderness into built environment such as settlements and semi-natural habitats such as arable fields, pastures, and managed woods. Land use by humans has a long history, first emerging more than 10,000 years ago. It has been defined as "the purposes and activities through which people interact with land and terrestrial ecosystems" and as "the total of arrangements, activities, and inputs that people undertake in a certain land type." Land use is one of the most important drivers of global environmental change. History Human tribes since prehistory have segregated land into territories to control the use of land. Today, the total arable land is 10.7% of the land surface, with 1.3% being permanent cropland. Regulation Land use practices vary considerably across the world. The United Nations' Food and Agriculture Organization Water Development Division explains that "Land use concerns the produ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Moisture
Soil moisture is the water content of the soil. It can be expressed in terms of volume or weight. Soil moisture measurement can be based on ''in situ'' probes (e.g., capacitance probes, neutron probes) or remote sensing methods. Water that enters a field is removed from a field by runoff, drainage, evaporation or transpiration. Runoff is the water that flows on the surface to the edge of the field; drainage is the water that flows through the soil downward or toward the edge of the field underground; evaporative water loss from a field is that part of the water that evaporates into the atmosphere directly from the field's surface; transpiration is the loss of water from the field by its evaporation from the plant itself. Water affects soil formation, structure, stability and erosion but is of primary concern with respect to plant growth. Water is essential to plants for four reasons: # It constitutes 80%-95% of the plant's protoplasm. # It is essential for photosynthesis. # It i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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